GaN film optical nonlinearity: wavelength dependent refractive index for All-Optical switching application.

• Good quality GaN film fabricated by MOCVD is confirmed via FESEM, EDS, AFM, XRD, UV–Vis and PL analysis. • Z-scan reveals the nonlinear absorption and nonlinear refraction properties of GaN thin film via 440 nm, 637 nm and 808 nm laser. • We detected a reversal of polarity of the nonlinear refractive index, n 2 at 637 nm and 405 nm of CW laser excitation and femtosecond laser pulse at 808 nm. • Novel all-optical dual beam switching scheme based on n 2 sign switchover of GaN is proposed. Gallium Nitride (GaN) is fast becoming a potential replacement for silicon in complex electronic and photonics circuitries and systems. At higher optical intensity, optical effects such as non-linear effects would become non-trivial. To this end, we investigated nonlinear optical properties of metal–organic chemical vapor deposited GaN. Specifically, continuous-wave laser Z-scan techniques were employed to obtain nonlinear refractive index, n 2 , of a 1-µm thin layer on a c-plane sapphire substrate. FESEM, PL, XRD and EDS analysis confirmed the good quality growth of GaN thin film. We detected a reversal of polarity of the n 2 value at 637 nm and 405 nm of CW laser excitation and femtosecond laser pulse at 808 nm. This is substantiated by theoretical calculation of GaN's n 2 showing sign switchover at wavelength shorter than 420 nm. This presents a new all-optical switching scheme based on the switchover of wavelength dependent n 2. These findings point to opportunities for GaN-based integrated photonics for nonlinear and quantum photonics applications. [ABSTRACT FROM AUTHOR]